Expulsion fuse switch



0d. 17, 1950 I l T. BIRKENMAIER 2,525,999

EXPULSION FUSE SWITCH 2 Sheets-Sheet 1 F119;: Nov. 28', 1947 Oct. 17, 1950 1 'r. B|RKENMAIER EXFULSION FUSE swrrcu 2 Sheets-Sheet 2 Filed Nov. 28, 1947 Patented Oct. 17, 1950 EXPULSION FUSE SWITCH Theodore Birkenmaier, St. Louis, Mo., assignor to W. N. Matthews Corporation, St. Louis, Mo., a corporation of Missouri Application November 28, 1947, Serial No. 788,481

6 Claims.

This invention relates to expulsion fuse switches, and with regard to certain more specific features, to enclosed fuse switches in which expulsion fuse elements are carried upon an automatically opening door.

Among the several objects of the invention may be noted the provision of a simple latching means for positively holding an expulsion fuse tube assembly on a door in a position for operation as a closing switch; the provision of a latchingmeans of the class described which is sensitive enough so that upon release of a fusible element therein movement of the expulsion tube with respect to the door, and movement of the door with respect to the enclosure will be effected surely; the provision of a switch of this class which while sensitive as to release conditions is nevertheless positively maintained closed under no-release conditions without unduly straining its fusible element; and the provision of apparatus of this class in which expended link parts are effectively withdrawn from the expulsion tube and in which contact damage due to arcing is minimized. Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

Fig. 1 is a longitudinal section of a fuse box embodying the invention, certain internal parts being shown in elevation;

Fig. 2 is a view similar to Fig. 1 but showin the arrangement of parts during a releasing operation;

Fig. 3 is a view similar to Figs. 1 and 2 but showing a final position of parts after a releasing operation;

Fig. 4 is an inside view of a switch door incorporating fuse parts in their non-released positions;

Fig. 5 is a view of the fuse box from which the door of Fig. 4 has been removed;

Fig. 6 is a cross section taken on line 3 of Fig. 1; and, I I

Fig. '7 is a cross section taken on line I-l of Fig. 2.

Similar reference characters indicate corresponding parts throughout'the several views of the drawings.

Referring now more particularly to the drawings, numeral I shows an insulating fuse box composed, for example, of porcelain. The box i is mounted upon a bracket 3, preferably in such a manner as to slope forward, as indicated. This box is enclosed by two sides 5 and I. It has a bottom opening 9 and a closed top II. On the forward side of the opening 9 and at the lower end of the box is carried a pivot pin i3 for a rotary door and fuse support IS. The door l5 carries a lower open hook portion I! for effecting a quick-detachable connection with the pin i3 when the door is inverted (see Fig. 3). The door also carries an eye l9, forming means by which it may be caught by hand or a tool for hinging action on the pin i3. In Figs. 1 and 2 the door is shown shut, and in Fig. 3 it is shown open and depending. In the Fig. 3 position the door may be removed from the box by raising it from the pin i3. As separated, it will appear as shown in Fig. 4.

The door is made of suitable insulating material such as one of the usual molded plastics, and includes an inside lug 2i in which is an opening 23 for slidably receiving an insulating fibre expulsion fuse tube 25. The fuse tube carries an upper conductive terminal-engaging element 21. It also carries a lower conductive terminal-engaging element 29. Both of the elements 21 and 29 are rigidly fastened to the tube 25, the upper one being threaded into position, as shown, and the lower one being held by means of a set screw, as shown. Attached to the upper element 21 is a pad 3|, which is slidable upon a flat pad 33 fastened to the door IS. The pad 33 includes an upper motion-limiting stop 35 for the upper edge of the pad 3|. These pads 3| and 33 may be made of conducting material such as a metal, if desired, the door itself being made of insulating material and providing desired insulation.

Aflixed to the lower terminal-engaging element 29 is a pad 31 formed of insulating material. This pad 31 is slidably carried upon two rail portions 39 forming a molded part of the door IS. A piece 4i attached to the bottom of the slide 31 forms a straight-line guide between the tongues 39. In view of the above it will be clear that the expulsion tube 25 is slidable up and down on the door l5.

The upper terminal-engaging element 21 at the upper end of the tube 25 is engageable with a spring clip 43 of an upper line terminal 56 in the box I. The clip 43 is in conductive relation to a lead-in socket 45 for the reception of a line wire 41 which enters through a suitable opening in the box I. The sides of the terminal-engaging element 21 are flat but flare outward and downward as indicated at numerals 88. The spring clip 88 has wing portions 8| which for conductive contact are likewise flared. These wings are also flared toward the front of the box,,as indicated at 88, for guiding reception of the engaging element 81. An auxiliary spring clip 88 is attached to the upper terminal 88 for engaging the flat back of element 21.

Toward the bottom of the box is mounted a second line terminal 81, which includes a spring clip 88 having downwardly flaring faces 8|. These faces also flare forward toward the door. The lower terminal-engaging element 28, which is adapted to engage with the lower line terminal, includes faces 88 which are also flared downward and outward toward the door for contact engagement with the faces 8|. The lower line terminal 81 includes a socket 88 for the reception of a second line wire 81 through a suitable opening in the box I. On the terminal 81 is supported an auxiliary spring clip 88 with which is adapted to engage a conducting holding screw II on the lower terminal-engaging element 28.

On the holding screw 1| is a holding nut 18 for anchoring the end of a flexible braided cable 15. This cable forms part of a fuse link 88. The other end of this link comprises a stiff section 18 and a head 88 which rests in an openable socket portion of the upper terminal-engaging element 81. The head 88 is held in place by a screw cap 11 for the socket. This fuse link includes a fusible portion section 18 around which is located a fibre tube 18 in the manner well-known in this art. This fusible section may or may not include a strain wire, depending upon the particular type of fuse link used. The tube 18 comes loose when the section 18 fuses. As indicated in the drawings, the fuse tube 28 extends downward past terminal 81 to a point adjacent the box opening 8, where it is provided with a notched opening 8|.

Pivoted to the rails 88 are the legs 82 of a fork 88. This fork includes at its outer movable end a snubber pad 88 having rounded edges 81. The fuse link is looped around edges 81 of this snubber pad 88. The pad 88 is in the region of the notch 8|, so that when the fork 88 is rotated upward clockwise (Fig. 1) the pad may follow the upper portion of the notch but does not necessarily engage it, as will be shown.

Attached to one leg of the fork 88 is a camming elevator latch 88. Its camming elevator portion 88 is on one side of it and its latchin portion 82 is on its upper end. This latch is engageable with a follower piece 8| attached to the 'slide 81. When the fork 88 is rotated clockwise,

assuming the fuse tube assembly to be down, the cam portion 88 engages the follower 8| to force up the fuse tube assembly. Ultimately the latch portion 82 slips under the follower 8| to latch up the fuse assembly on the door. To maintain the fork 88 in the holding position the flexible cable II of the fuse link 88, which emerges from the notched opening 8|, is looped around the snubber pad 88 and then under the nut 18, where it is fastened. This holds the latch portion 82 under the follower 8|. Any force tending to push down the tube assembly is applied to the fork 88 on a relatively short lever arm around its pivoting outer (pin 88). The resisting moment provided by the link portion 18 looped around pad 88 is therefore relatively small, which means that the fusible element 18 or any strain wire associated therewith is protected from excessive me- 4 chanical loading. In this connection it will be noted that the pad 88 preferably has no engagement with the notch 8|.

The box intermediate its ends has an inside septum |8| in which is a notch I88 which lies around the fuse tube 28 when the door I8 is closed. This acts as a means for increasing the leakage path of current between the line terminals 88 and 81.

Operation is as follows:

A fuse link 88 is threaded, flexible end 18 first, through the fuse tube 88, the head 88 of the link flnally seating on the open upper end of the socket part of element 81. The cap 11 is then screwed in place. The fork 88 is then pushed up manually, which through action of the cam 88 on follower 8|, moves the fuse tube assembly upward on the door II. The fuse link is then looped around the snubber pad 88 and around screw 1|,

being then fastened by means of the nut 18. This places the door and fuse parts in the assembled position shown in Fig. 4.

The door is then inverted and its hook l1 applied to pin i8. It is then rotated into circuitclosing position (Fig. 1). The terminal-engaging elements 21 and 28 engage the line terminal clips 88 and 88, respectively. Friction between these holds the door shut. At the same time, the clips bias the tube assembly downward and consequently also the door, reaction being provided by the pin I8. Relative motion between the tube assembly and the door is prevented by the catch portion 82 cooperating with the follower 8|. A considerable force may be applied without unduly tensioning the fuse link. Excellent electrical contact may thus be maintained at the line terminals under substantial pressure without deleteriously tensioning the fuse link. Hence under the stated conditions, the auxiliary spring clips 88 and 88 of the line terminals are in good conductive relation with the terminal-engaging elements 21 and 28, respectively.

Upon blowing of the fuse link (fusing of the fusi ble element 18 under excessive current), the slight holding action of the flexible leads 18 on the pad 88 is released. The overhanging weight of the fork 88 and pad 88 pulls the catch 82 from under the follower 8|. The weight of the sliding fuse tube assembly (which includes the fuse tube and attached terminal-engaging elements) causes the follower 8| to slide down the cam 88, acting as a wedge to rotate the fork downward relative to the tube. This strips the lower portion of the flexible cable 18 out of the lower end of the tube 28, assisted by the expulsive action of the gases formed by vaporization of the fusible element 18. Finally, the line terminals 21 and 28 disengage from the terminal clips 88 and 88. respectively.

The auxiliary spring clips 88 and 88 temporarily maintain the circuit during the period that arcing occurs across the separated ends of the fuse link. As this are is attenuated and broken (with increased separation), the engagement of the terminal-engaging elements with the auxiliary contacts 88 and 88. respectively, is temporarily maintained after contact has been broken between the terminal-engaging elements and the clips 88 and 88, respectively. Thus all frictional contact holding action on the door is at this time eliminated. Consequently. Bravity, assisted by the outward pressure of the auxiliary contacts 88 and 88 forces the door open, which will gravitationally rotate to the open position shown in Fig. 3. The circuit connected across the line terminals 88 and 81 is then positively completely open with a clearl readable signal of this fact given by the downwardl hanging door. To reclose the circuit, the door is unhooked from the pin ll and re-fused, and is then again hooked into position and reclosed, as above made clear.

Advantages of the invention are that with a simple mechanical structure which is little subject to derangement, high electrical contact pressures may be maintained under normal conditions without unduly stressing the fusible element It in the fuse link. Thus less dependence needs to be placed upon the so-called strain wires which are commonly connected in parallel with the fusible elements. Also, lower stresses are involved in the fusible element, if used alone.

The cammlng action of the follower ll upon the cam portion 90 results in a multiplied movement of the pad 85 during an expulsive action, which provides a relatively large movement of the pad for instantly strip a relatively large amount of the flexible element II from inside of the tube 25. Large movement is increased by the fact that the general plane of the snubber I! is normal to the tube axis and extends a substantial distance from that axis. The result is that the switch does not tend to hang" shut upon fusing action.

When the terminal-engaging elements 21 and 29 separate from the clips 43 and 59, respectively, the door is quite free to swing open, particularly inasmuch as it is assisted by an initial pushing action from the auxiliary clips 55 and 89. These clips also maintain the line circuit until the blowing fuse arc expends itself, thereby preventing arcing between the terminal-engaging elements and the line terminal clips 43 and I9. Furthermore, should the are be slow in extinguishment, any are that might be formed as the door opens is drawn at the auxiliary terminals 58 and 69, which are less costly to replace than the clips 43 and 59. Besides, it is desirable to have the surfaces of these clips ll and 59 always unburned and in smooth condition for proper mechanical contact and release functions. However, slow extinguishment will seldom occur in view of the quick withdrawal of the blown fuse elements from the tube by the motion-multiplying action between the cam portion 00 and the extracting D d 85.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results obtained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A fuse switch comprising two line terminal spring clips both of which flare downward, a rotary fuse support movable from a depending to a raised position, a fuse tube assembly slidable on said support and having two terminal-engaging elements also flared downward and respectively frictionally engageable with said clips when the assembly is in a raised position on the support so as firmly to hold up the support. a fuse for mechanically holding said assembly in said position and adapted upon fusing to release said assembly to be pushed by the clips into another position wherein said terminal-engaging elements are both completely separated from the clips whereby the support may freely rotate to its de- 6 pending position, said flaring forms of the spring clips both urging the flaring terminal-engaging elements completely therefrom.

2. A fuse switch comprising two contact spring clips both of which flare downward, a pivoted fuse support movable from a depending to a raised position, a fuse tube assembly slidable up and down on said support with respect to its pivot point and having two terminal-engaging elements also flared downward and respectively frictionally engageable with said clips when the assembly is in a raised position on the support so as firmly to hold up the support, a fuse for mechanicallyholding said tube assembly in said position and adapted upon fusing to release said assembly to drop into another position wherein said terminal-engaging elements are both completely separated from the clips to release the support whereby the support may freely rotate to its depending position, said flaring forms of the spring clips urging both of the flaring terminal-engaging elements therefrom, and two auxiliary contacts respectively associated with the contact clips biasing the terminal-engaging elements to pivot the fuse support, said auxiliary contacts temporarily maintaining contact with the terminal-engaging elements after the latter separate from the clips and release the support.

3. A fuse switch comprising a box having an open front and two line-terminal clips both of which flare downward, one of said clips also flaring toward the door, a door hinged to the box for closing said front, a fuse tube assembly slidable on said door and having two terminal-engaging elements also both flaredv downward and one outward and respectively frictionally engageable with said line terminals when the assembly is held in raised position on the door and the door is shut whereby the door is flrmly held shut, said terminal-engaging elements being completely separable from the terminal clips by the action of said clips when the assembly is released from its held position, an operating element for holding said assembly in said raised position, and a fuse which normally holds said element but upon fusing releases it to release the assembly, whereby the door may freely pivot from its closed to an open position.

4. A fuse switch comprising a box having an open front and bottom and also line-terminal clips which flare downward and toward the open front, a door removably hinged to the box for closing said front, a fuse tube assembly slidable on said door and having terminal-engaging elements also flared downward and frictionally engageable with said clips when the assembly is raised on the door and the door is shut, a cam and latch member pivoted to the door below the terminal-engaging elements, a follower on the fuse tube assembly engageable with said cam and latch member, whereby the tube assembly moves up and becomes latched up on the door in response to a predetermined positioning of the cam and latch member, said cam and latch member including a snubber, said fuse tube assembly having a lower opening adjacent the snubber and a flexible fuse element extending from said opening and adapted to be looped around said snubber and fastened to the lowermost of said terminal-engaging elements to hold the cam and latch member in latching position.

5. A fuse switch comprising a box having an open front and bottom and also a pair of downwardly biasing line-terminal clips, a door hinged 7 at the bottom to the box for closing said front, a fuse tube assembly which is open at its lower end, slidable on said door and having a pair of terminal-engaging elements frictionally engageable under said clips when the assembly is raised on the door and the door is moved to a closed position, said elements being pushed entirely clear by the clips when the assembly drops, a snubber mechanism pivoted to the door and movable at the open end of said assembly to a raised position holding up the fuse tube assembly, a flexible fuse link extending between said terminal-engaging elements and through said opening and looping said snubber mechanism to hold the latter in the position wherein it holds up the fuse tube assembly when the fuse link is unblown, whereby the terminal-engaging elements are firmly frictionally held under the line-terminal clips firmly to hold the door shut after the latter is closed, the snubber mechanism upon blowing of the fuse being released to release the terminal-engaging elements so that the downward bias of the lineterminal clips entirely removes both of the terminal-engaging elements therefrom, whereby the door may swing freely to open position without any friction between the line-terminal clips and the terminal-engaging elements.

6. A fuse switch comprising a box having an open front and bottom and also line-terminal clips both of which flare downward, a door hinged 3 when the assembly is raised on the door and the 8 doorismovedtoaelosedpoaitiomasnubber pivoted to the door and movable at the open end of said assembly, a latch movable by and with the snubber, a follower on the assembly engageable by the latch to hold the assembly in elevated position on the door, a flexible fuse link extending between said terminal-engaging elements and through said opening and looping said snubber to hold the latter when the fuse link is unblown in the position wherein the latch holds up the fuse tube assembly, so that the terminalengaging elements are firmly frictions-11y held by the line-terminal clips firmly to hold the door shut after the latter is closed, the snubber upon blowing of the fuse being released thereby to release the latch so that downward forces due to the flares of the line-terminal clips downwardly completely remove both of the terminal-engaging elements therefrom, whereby the door may freely swing to open position without any friction between the line-terminal clips and the terminalengaging elements.

THEODORE B.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,098,433 Schultz NOV. 9, 1937 2,176,045 Birkenmaier Oct. 17, 1989 2,231,510 Schultz Feb. 11, 1941 2,249,178 Schultz July 15, 1941 

